Bloodied and bowed, Richie McCaw staggers from the field. The staples in his face and the blood on the silver fern that adorns his shirt point to a bruising battle while his expression hints that the effort was in vain.

The image, captured by Ross Land in the aftermath of New Zealand's narrow defeat to South Africa in Rustenburg in 2006 and featured in a recently published book entitled Union: The Heart of Rugby, highlights the warrior-like qualities that have formed the bedrock of McCaw's glittering 10-year international career.

His legendary status was cemented with his 100th Test cap earlier this month - the first All Black to reach such a milestone. The modest flanker, who will turn 31 on New Years' Eve, was the subject of widespread praise while highlights of his decade at the top of the game filled airwaves and column inches - but it is not the three International Rugby Board Player of the Year awards or the Tri-Nations titles that will drive him on in search of the major accolade missing from his rugby CV, the World Cup, it is dark days such as this.

When your career has been blessed with so much success then the failures will almost take precedence in any recollection. For McCaw, the World Cup semi-final defeat to Australia in 2003 and the quarter-final exit at the hands of France four years later must surely loom larger in his memory than in the minds of those fans heartbroken as a result. Just like the now injured fly-half Dan Carter, everything that he has done on a rugby field since that shock defeat at the Millennium Stadium in 2007 has been geared towards this tournament. The demands he will no doubt put on himself will surely bring as much pressure as the nation's hopes that he will also shoulder.

What will concern those same fans is the injury cloud that hovers over their captain. McCaw was sidelined for the start of the Crusaders' Super Rugby campaign after suffering a stress fracture in his right foot during pre-season and had a screw inserted into his fifth metatarsal to aid recovery. "The injury is obviously disappointing but it's not likely to be one that will bother me in the long term," he said at the time but here we are eight months later and it is still obviously troubling him.

He featured in the tournament opener against Tonga and in the quarter-final clinching victory over France and while it was a calf strain that sidelined him for the game against Japan, it was the foot complaint that returned to deny him an appearance against Canada. By now it was all about managing the injury. "It's something I have managed all the way through. If I had to play a knockout game tomorrow night I would," insisted McCaw but how about three knock out games in successive weeks?

He returned to training ahead of the quarter-final date with Argentina on Sunday but the more observant will have seen he was wearing trainers when others were booted up. There is no room for passengers at the business end of the tournament no matter what they may offer when fit. Being half a yard off the pace of the game or distracted by doubt for even a fraction of a second could prove costly.

Unsurprisingly McCaw's stop-start season has had an impact on his form with many predicting the end to his dominance. Unable to get his Crusaders past the Reds in the Super Rugby season finale he was also on the wrong side of the result with the All Blacks in their Tri-Nations title decider with Australia. During this World Cup he has also seen other openside flankers steal the limelight with familiar foes in the form of Australia's David Pocock and South Africa's Heinrich Brussow joined by rising stars in the shape of Wales' Sam Warburton and Ireland's Sean O'Brien.

To his credit, McCaw has changed his game over the years as the nature of the breakdown and how it is managed has evolved. But it would it appear now that the gap in terms of performance and excellence between McCaw and his rivals appears closer than ever. Brussow has yet to taste defeat in four head-to-heads with his Kiwi counterpart while Pocock also had the beating of McCaw in their latest confrontation in Brisbane in August. As a result, neither will fear the prospect of another titanic tussle if the semi-final line-up demands so.

But of course, McCaw is so much more than just the guy who wears the No.7 on his back. No one has led the All Blacks as many times (63) or been as successful. The All Blacks have tasted defeat just eight times with McCaw at the helm while only 12 losses blight his century of Test appearances. And he is not try-shy either with a record 19 scores to his name.

For many he is the greatest ever All Black, although those with longer memories still hold Colin 'Pintree' Meads and Buck Shelford dear, but what cannot be denied is that New Zealand's chances of ending their World Cup drought are significantly better with McCaw in their ranks. That is why he simply has to be at the heart of their push for glory.

With Carter sidelined, McCaw's inspirational presence is more vital than ever before in the All Blacks' recent history. Just like the staples that held his rugged features together on that fruitless day in Rustenburg, he is the bond that binds this talented group of individuals together. And just like on that blood-soaked occasion, expect him to play through the pain barrier in search of the ultimate prize.